The successful construction of engineered tissues requires the re-creation of a biologically active extracellular environment in which to develop the product. Ultrasound therapy is currently used clinically to promote bone healing and has been shown to enhance soft tissue repair. Some biological effects of ultrasound are known to result from the mechanical forces associated with acoustic wave propagation. In vitro studies demonstrate that mechanical stresses positively affect both extracellular matrix (ECM) organization and cell behavior. Thus, we hypothesize that acoustically-driven mechanical forces can be used to control ECM deposition and promote cell and tissue function. In this proposal, we combine our knowledge of ECM biology and biomedical ultrasound to develop ultrasound-based enabling technologies for the fabrication and monitoring of functional 3D ECM and tissue analogs. To accomplish this goal, we have developed four specific aims. In Aim 1, we will use ultrasound fields to fabricate ECM FN and collagen analogs, and optimize ultrasound exposure conditions that enhance ECM-mediated fibroblast and epithelial cell growth. In Aim 2, we will develop the use of acoustically-driven mechanical forces to promote fibroblast migration into 3D, collagen- based tissue constructs. In Aim 3, we will use acoustic fields to stimulate ECM organization in order to engineer the biological and material properties of collagen-based tissue constructs. In Aim 4, we will apply and extend our experience in ultrasound tissue characterization technologies to non-destructively quantify mechanical and biological properties of engineered tissues in real-time. We envision immense potential for the use of ultrasound technologies to provide break-through technologies for tissue fabrication and monitoring. Furthermore, the ability of ultrasound to propagate through tissue as a focused beam has the potential to provide a revolutionary approach to locally regulate and monitor tissue regeneration deep within the body. Tissue engineering is a potentially revolutionary approach for replacing or regenerating diseased or destroyed organs and tissues. The current lack of available tissue analogs reflects an inability to create 3-D scaffolds that have both biological activity and adequate mechanical strength. We will develop ultrasound- based enabling technologies with the dual capacity to (i) create biologically-active, 3-D tissue constructs for tissue engineering and (ii) non-invasively monitor the biological and mechanical properties of these constructs. (End of Abstract)